GIGANTOCYPRIS MULLERI 233 



assuming that this is really one ganglion on either side serving the two muscles. Down 

 the aorta the ganglia extend on each side as elongated structures narrowing to a point 

 where they penetrate the aortic floor and immediately join the dorsal surface of the 

 brain (Figs. 12, 16). Throughout the whole ganglion numerous connexions are being 

 made with the muscles. 



This aortic ganglion system is a new development in Gigantocyprh . In Doloria 

 I figured a median nerve from the stomach ganglion which I stated (p. 471) "can be 

 traced to the aortic roof and the pericardial dilator". I could not trace it further than 

 the aortic tendon and hence deduced that it supplied the two muscles extending upwards 

 from this. I now think that it probably has no connexion with the pericardial dilator 

 and serves only the aortic muscles. In Gigantocypris it connects through the aortic 

 ganglia with the aortic muscles from their origin at the aortic tendon upwards (Fig. 16). 

 It however has no connexion with the pericardial dilator. The latter appears to be without 

 a separate nerve supply. 



The morphological facts suggest strongly that the pericardial dilator is an independent 

 effector organ. Although attached to the same tendon ventrally as the aortic muscle, 

 I pointed out that in Doloria the pericardial dilator must work in opposition to the 

 latter muscle (1931, p. 459). This would fit in with the fact that while the latter has 

 such a marked nerve supply the former has none. Further, the striations of the pericardial 

 dilator are extremely simple. In fact, I call it a muscle merely because it shows alter- 

 nating bands of staining and non-staining substance. But these bands are not at all 

 sharply marked from each other. I have repeatedly remarked that in the Crustacean 

 body it is possible to find all stages of the transition from connective tissue cells showing 

 longitudinal striations to typical striated muscles, the stages, in fact, that are exhibited 

 in the embryology of ordinary striped muscles (Cannon, 1926, p. 414). The pericardial 

 dilator of Gigantocypris represents a morphological level about the middle of this series. 

 At the beginning of the series it would not be expected that the connective tissue cells 

 would of necessity have their own motor supply. At the other end of the series one 

 would naturally expect a direct nerve supply. The pericardial dilator, I suggest, repre- 

 sents a stage in the evolution of a contractile system before this direct nervous control 



appeared. 



There is, of course, the possibility that the nerve supply to this muscle is extremely 

 fine and cannot be demonstrated by the methods I have used. This certainly may be so, 

 but a point against such an assumption is the fact that it is possible to trace the nerve 

 supply of practically every muscle of the body, and always the nerve ending is the same. 

 It is a little pillar of protoplasm which spreads out on the effector organ and is of the 

 size indicated in the text figures, that is, of a size easy to see and in fact difficult to 



overlook. m ^ ^ 



INTERNAL STRUCTURE 



As regards the internal structure of the central nervous system, I am describing 

 only those points which appear significant in comparison with the account which I gave 

 of the nervous system of Doloria (1931, p. 47 2 )- 



